Multicast Snooping on MX Series Routers

Because MX Series routers can support both Layer 3 and Layer 2 functions at the same time, you can configure the Layer 3 multicast protocols Protocol Independent Multicast (PIM) and the Internet Group Membership Protocol (IGMP) as well as Layer 2 VLANs on an MX Series router.

Normal encapsulation rules restrict Layer 2 processing to accessing information in the frame header and Layer 3 processing to accessing information in the packet header. However, in some cases, an interface running a Layer 2 protocol needs information available only at Layer 3. In multicast applications, the VLANs need the group membership information and multicast tree information available to the Layer 3 IGMP and PIM protocols. In these cases, the Layer 3 configurations can use PIM or IGMP snooping to provide the needed information at the VLAN level.

For information about configuring multicast snooping for the operational details of a Layer 3 protocol on behalf of a Layer 2 spanning-tree protocol process, see Understanding Multicast Snooping and VPLS Root Protection.

Snooping configuration statements and examples are not included in the Junos OS Layer 2 Switching and Bridging Library for Routing Devices. For more information about configuring PIM and IGMP snooping, see the Junos OS Multicast Protocols User Guide.